Strain Criterion of Reheat Cracking in 2.25Cr1Mo0.25V Steel
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摘要: 在不同参数下制备了2.25Cr1Mo0.25V钢焊接接头热影响区粗晶区（CGHAZ）的热模拟试样，通过与实焊接头CGHAZ硬度、晶粒度和组织的对比，确定最佳热模拟参数；采用该参数得到模拟CGHAZ试样，研究了其在675℃下的应力松弛行为，分析了再热开裂过程并得到再热开裂应变判据。结果表明：最佳热模拟参数为热输入30 kJ·cm-1、预热温度200℃、加热速率1 000℃·s-1、峰值温度1 320℃、峰值温度停留时间1 s，所得CGHAZ试样的组织为板条贝氏体，晶粒度级别为4.5级；CGHAZ试样在不同初始应力下的应力松弛行为相似，其临界失效蠕变应变均在0.31%左右；该临界失效蠕变应变可视为再热开裂应变判据，也可作为表征CGHAZ再热裂纹敏感程度的蠕变应变分界点，用于评价该钢的焊后热处理工艺。
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关键词:
- 2.25Cr1Mo0.25V钢 /
- 热影响区粗晶区(CGHAZ) /
- 再热裂纹 /
- 热模拟 /
- 应变判据
Abstract: Coarse-grained heat-affected zone (CGHAZ) simulation specimens of 2.25Cr1Mo0.25V steel welded joint were prepared with different parameters, and the optimal thermal simulation parameters were determined by comparing hardness, grain size and microstructure with those of the actual joint CGHAZ. And then the CGHAZ specimen was simulated with the optimal parameters. The stress relaxation behavior of the specimen at 675℃ was studied, the reheat cracking process was analyzed, and the reheat cracking strain criterion was obtained. The results show that the optimal thermal simulation parameters were listed as follows:heat input of 30 kJ·cm-1, preheating temperature of 200℃, heating rate of 1 000℃·s-1, peak temperature of 1 320℃, time on peak temperature of 1 s. The microstructure of the obtained CGHAZ specimen consisted of lath bainite, with grain size of grade 4.5. The stress relaxation behaviors of CGHAZ specimen were similar under different initial stresses. The critical failure creep strains were all about 0.31%. The critical failure creep strain can be regarded as the reheat cracking strain criterion, and can be used to evaluate the post-welding heat treatment process of the steel as the creep strain demarcation point for characterizing the sensitivity of CGHAZ reheat crack. -
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